Mechanical, Magnetic, and Microstructural Characterization of Ni0.9Co0.1Fe2O4 Produced by the Ceramic Method

Abstract

Ni-Co ferrites, especially the ones with lower cobalt fractions, are candidate materials for applications in magnetomechanical sensors and electromagnetic wave absorbers. This work studied the microstructure, magnetostriction, flexural strength, and complex magnetic permeability of Ni 0.9 Co 0.1 Fe 2 O 4 , presenting data that weren't covered by previous literature on this composition. It was found that sieving the calcined powder before the forming operation increased the flexural strength of the ceramic. The Ni-Co ferrite had a saturation magnetostriction of 36ppm. The real part of the complex magnetic permeability varied between 2.2-2.3 in frequencies from 100MHz to 1GHz. In frequencies higher than 1GHz, µ' decreased sharply and reached 1 at 3.9GHz. It was found that the grinding media provided a small fraction of Al to the ferrite composition, which apparently affected the complex magnetic permeability of the material but the magnetostriction results were very close to Al-free Ni-Co ferrites with similar composition.

Sintering of layered ferrite-BaTiO3 ceramics: Analysis of interfaces and effects of shrinkage mismatch

“…Density (ρ) of pressed and sintered pellets was determined from sample mass m measured with an analytical balance and volume V (dimensions were measured with a DIGIMESS 400.400 profile projector) by the following equation ρ = m/V. Relative density (ρ r = ρ/ρ theo ) was calculated by using the following theoretical densities (ρ theo ): 6.02 g/cm 3 for TB [26], 5.35 g/cm 3 for FCO and 5.39 g/cm 3 for FNICO (obtained according to XRD data [27] and considering 8.36 Å and 8.33 Å as lattice parameters of FCO and FNICO, respectively). The microstructure and the phase composition were evaluated from one sample for each sintering temperature.…”